The present invention relates to an improved device for preheating substrates for a coating process that requires preheating of the substrates. It also relates to an improved coating method in which substrate preheating is required. The invention also relates to an external preheating of the substrates.
U.S. Pat. No. 5,976,258 discloses an apparatus for processing substrates. The apparatus contains a component for heating of the substrates to an elevated temperature. The substrate is pre-heated there and then transported or conveyed for further processing.
Substrate holders with recesses are disclosed in U.S. Pat. No. 4,350,578, U.S. Pat. No. 5,137,610 and JP-A-01-255671.
In the conventional method for preheating substrates, especially glass parts, prior to coating them, the preheating is energy-intensive and time-consuming.
It is an object of the present invention to provide an improved coating process in which preheating of the substrates to be coated is required.
It is another object of the present invention to provide an improved economic, environmentally friendly method for preheating substrates to be coated in a coating process.
It is a further object of the present invention to provide a heating device for preheating substrates for a coating process requiring preheating of the substrates.
The method according to the invention of coating a substrate in which preheating of the substrate is required comprises the steps of:
a) providing a device for heating the substrate, which includes at least one heat-producing component and at least one glass-ceramic plate, wherein the at least one glass-ceramic plate is provided with at least one recess and the substrate fits in the at least one recess so as to be on said at least one heat-producing component;
b) placing the substrate in the at least one recess so that a surface of the substrate to be coated is placed on the at least one heat-producing component;
c) heating the substrate from below to a process temperature required for the coating with the at least one heat-producing component; and
d) removing the substrate from the device for the heating and then placing the substrate in a coating chamber; and subsequently
e) coating the substrate in the coating chamber.
The heating device according to the invention for preheating the substrates considerably shortens the time required for coating the substrate. The overall process including coating and preheating saves energy. The preheating reduces wear of the coating device. The preheating of the substrate is more uniform when the preheating device according to the invention is used. The quality of the coating is improved in the coating process according to the invention. The temperature adjustment required can be implemented without influencing the process time. The coating process according to the invention facilitates stable process management.
In a preferred embodiment of the invention the heating device includes at least one heat-producing component and at least one glass-ceramic plate. The at least one glass-ceramic plate is provided with at least one recess in which the substrate fits or which matches the substrate. Because of its low thermal conductivity, the glass-ceramic material is preferred for the plate or plates.
A preferred embodiment of the heating device according to the invention has two glass-ceramic plates, which are laid loosely on top of one another, and have correspondingly different recesses with different sized openings arranged approximately over each other. The approximately coincident recesses in the respective plates provide substrate receptacles. When the heating device comprises the two glass-ceramic plates, heat losses are correspondingly reduced. The production of the substrate receptacles is made easier.
In a preferred embodiment of the coating method according to the invention during the preheating of the substrates the internal temperature of the heating device is from 500xc2x0 C. to 800xc2x0 C. Good results are achieved within this temperature range. According to another preferred embodiment of the method at least one coating layer is provided on the substrate to be coated by the coating method.
According to various embodiments of the coating method of the invention, the coating of the substrates is performed by at least one of the following processes: CVD (chemical vapor deposition), PVD (physical vapor deposition), PECVD (plasma-enhanced chemical vapor deposition), PICVD (plasma impulse chemical vapor deposition), LPCVD (low-pressure chemical vapor deposition) or TCVD (thermal chemical vapor deposition).
In a preferred embodiment of the device according to the invention the heat-producing components are infrared high-temperature radiators. These high-temperature radiators have a longer service life.
Glass substrates are especially preferred as the substrates.